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metrics.go
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metrics.go
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// Copyright (c) 2020 The Jaeger Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package httpmetrics
import (
"net/http"
"strconv"
"sync"
"time"
"go.uber.org/zap"
"github.com/jaegertracing/jaeger/pkg/metrics"
)
// limit the size of cache for timers to avoid DDOS.
const maxEntries = 1000
type statusRecorder struct {
http.ResponseWriter
status int
wroteHeader bool
}
func (r *statusRecorder) WriteHeader(status int) {
if r.wroteHeader {
return
}
r.status = status
r.wroteHeader = true
r.ResponseWriter.WriteHeader(status)
}
// Wrap returns a handler that wraps the provided one and emits metrics based on the HTTP requests and responses.
// It will record the HTTP response status, HTTP method, duration and path of the call.
// The duration will be reported in metrics.Timer and the rest will be labels on that timer.
//
// Do not use with HTTP endpoints that take parameters from URL path, such as `/user/{user_id}`,
// because they will result in high cardinality metrics.
func Wrap(h http.Handler, metricsFactory metrics.Factory, logger *zap.Logger) http.Handler {
timers := newRequestDurations(metricsFactory, logger)
return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
start := time.Now()
recorder := &statusRecorder{ResponseWriter: w}
h.ServeHTTP(recorder, r)
req := recordedRequest{
key: recordedRequestKey{
status: strconv.Itoa(recorder.status),
path: r.URL.Path,
method: r.Method,
},
duration: time.Since(start),
}
timers.record(req)
})
}
type recordedRequestKey struct {
method string
path string
status string
}
type recordedRequest struct {
key recordedRequestKey
duration time.Duration
}
type requestDurations struct {
lock sync.RWMutex
metrics metrics.Factory
logger *zap.Logger
maxEntries int
timers map[recordedRequestKey]metrics.Timer
fallback metrics.Timer
}
func newRequestDurations(metricsFactory metrics.Factory, logger *zap.Logger) *requestDurations {
r := &requestDurations{
timers: make(map[recordedRequestKey]metrics.Timer),
metrics: metricsFactory,
logger: logger,
maxEntries: maxEntries,
}
r.fallback = r.getTimer(recordedRequestKey{
method: "other",
path: "other",
status: "other",
})
return r
}
func (r *requestDurations) record(request recordedRequest) {
timer := r.getTimer(request.key)
timer.Record(request.duration)
}
func (r *requestDurations) getTimer(cacheKey recordedRequestKey) metrics.Timer {
r.lock.RLock()
timer, ok := r.timers[cacheKey]
size := len(r.timers)
r.lock.RUnlock()
if !ok {
if size >= r.maxEntries {
return r.fallback
}
r.lock.Lock()
timer, ok = r.timers[cacheKey]
if !ok {
timer = r.buildTimer(r.metrics, cacheKey)
r.timers[cacheKey] = timer
}
r.lock.Unlock()
}
return timer
}
func (r *requestDurations) buildTimer(metricsFactory metrics.Factory, key recordedRequestKey) (out metrics.Timer) {
// deal with https://github.com/jaegertracing/jaeger/issues/2944
defer func() {
if err := recover(); err != nil {
r.logger.Error("panic in metrics factory trying to create a timer", zap.Any("error", err))
out = metrics.NullTimer
}
}()
out = metricsFactory.Timer(metrics.TimerOptions{
Name: "http.request.duration",
Help: "Duration of HTTP requests",
Tags: map[string]string{
"status": key.status,
"path": key.path,
"method": key.method,
},
})
return
}